All new files uploaded result in 404 error page.

Last week everything was working fine. However, today, I went to upload (via most recent version of FileZilla) a file for a friend to download but he told me the link resulted in the WordPress 404 page. Tried it myself, and got the same. Thinking I mistyped, I renamed the file several times until it was just a.jpg. Still no luck!

The file above it, 1.gif, had been in there previously and loaded up just fine. I removed it and reuploaded it, and now receive a 404 error from it, as well.

I then uploaded a theme folder, and found WordPress didn’t see the new folder.

I have found that I can use WordPress’s uploader to upload files for posts, and that works just fine. I can navigate directly to the .jpg file and it loads outside of the main WP site, as well. Given this, I feel it’s a WP issue.

I’m really lost at what to do or try, so any help is appreciated!

Edit: I changed the Permalink structure to the base ?p=123 setup. And now I get the base server 404 page outside of WP. And if I right-click and save the link, it will download but cannot be opened.